Nuclear Quadrupole Coupling Constants

in trans-1-Chloropropene


Calculation of the chlorine nqcc's in trans-1-chloropropene was made on a molecular structure derived ab initio, as described below.  These are compared with the experimental nqcc's of Beaudet [1] in Table 1.  Structure parameters are given in Z-matrix format in Table 2.
In Table 1, RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation for the B1LYP/TZV(3df,2p) model for calculation of the chlorine nqcc's. 
Subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis, these are perpendicular to the molecular symmetry plane.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.



Table 1. Chlorine nqcc's in t-1-Chloropropene, conformer I (see below) (MHz).

Expt. [1]

35Cl Xaa - 60.67 - 60.3
Xbb 28.88 28.7
Xcc 31.79 31.6
|Xab| 31.13
RMS 0.3 (0.75 %)
RSD 0.49 (1.1 %)
Xxx 38.63
Xyy 31.79
Xzz - 70.43
ETA - 0.097
Øz,a 17.40
Øa,CCl 17.20
Øz,CCl   0.20
37Cl Xaa - 47.86
Xbb 22.80
Xcc 25.06
|Xab| 24.47
RSD 0.44 (1.1 %)

Cl is trans with respect to CH3.  Within the framework of Cs symmetry, one methyl H lies in the plane of symmetry, one above and one below the plane.  With respect to the C(1)C(2)C(3) backbone, the in-plane H may be trans (conformer I) or cis (conformer II) with Cl.  Calculation was made on both structures.  At the B1LYP/TZV(3df,2p) level of theory, EI < EII by 2.0 kcal/mol.  The calculated nqcc's shown in Table 1 are for conformer I, for which the RMS difference between calculated and experimental nqcc's is 0.3 MHz.  For conformer II, calculated Xaa, Xbb, and Xcc  are respectively -60.76, 28.95, and 31.80 MHz.  The RMS difference is, as above, 0.3 MHz.
Molecular Structure
The molecular structure was optimized at the MP2/6-311+G(d,p) level of theory assuming Cs symmetry.  The optimized CC bond lengths, single and double,  were corrected using equations obtained from linear regression analysis of the data given in Table IX of Ref.[2].  For the CCl bond, the structure was optimized at the MP2/6-311+G(2d,p) level and corrected by linear regression analysis of the data given in Table 4 of Ref.[3].  The CH bond lengths were corrected using r = 1.001 ropt, where ropt is obtained by MP2/6-31G(d,p) optimization [4].  Interatomic angles used in the calculation are those given by MP2/6-311+G(d,p) optimization.
Table 2.  Z-Matrix (Å and degrees).
C 1 R1
C 2 R2 1 A3
C 2 R3 1 A4 3 180.
Cl 4 R4 2 A5 3 180.
H 4 R5 2 A6 3     0.
H 3 R6 2 A7 6 D1
H 3 R7 2 A8 6 -D2
H 3 R7 2 A8 6 D2
Conformer I Conformer II
R1 1.0845 1.084
R2 1.4945 1.5035
R3 1.329 1.329
R4 1.726 1.726
R5 1.082 1.082
R6 1.090 1.088
R7  1.0915 1.091
A3 118.28 118.87
A4 119.04 118.56
A5 123.06 123.00
A6 123.36 123.47
A7 111.27 110.54
A8 110.71 111.45
D1     0. 180.
D2 120.40   60.29


[1] R.A.Beaudet, J.Chem.Phys. 37,2398(1962).
[2] J.Demaison, J.Cosléou, R.Bocquet, and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994).
[3] I.Merke, L.Poteau, G.Wlodarczak, A.Bouddou, and J.Demaison, J.Mol.Spectrosc. 177,232(1996).
[4] J.Demaison and G.Wlodarczak, Structural Chem. 5,57(1994).





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Last Modified 16 June 2004